The disclosure is directed to doped, ultra-low expansion (“ULE”) glass, glass articles and methods for making the same, including doped silica-titania ULE glass systems.
Extreme Ultra-Violet Lithography (“EUVL”) is the emerging/leading lithography technology for the 13 nm node and beyond for manufacturing Micro Processing Units (“MPU”) and Dynamic Random Access Memory (“DRAM”) chips. The EUVL scanners which are used to produce MPU, DRAM and other integrated chips are presently being produced in small numbers to demonstrate this technology. Projection optics systems, particularly reflective optics systems, are an important part of these scanners. Low thermal expansion glass, for example Corning® Incorporated ULE® glass, is currently being used for making the projection optics systems used in EUVL scanners. Advantages of a low thermal expansion glass such as ULE® Glass include: polishability to the required finish, coefficient of thermal expansion (“CTE”) and expansivity control, and dimensional stability.
As the development of EUVL systems proceeds, the specifications are becoming more stringent for newer optics systems, particularly those employed in high-volume integrated chip and semiconductor device manufacturing. As a result, the specifications for the materials employed in these optics systems, including CTE and expansivity criteria, are becoming increasingly more difficult to achieve. Accordingly, there is a need for ULE glass, and methods of making it, that can be employed in EUVL applications, for example.